This invention relates generally to ultrasonic dental tools and more specifically to special non-surgical ultrasonic root canal tools.
Dental surgeons commonly use a tool usually called a tip coupled to an ultrasonic generator for operations on teeth, bones, and soft tissue including dislodging and removal of dental material. The use of ultrasonic generators for powering tools for clinical dentistry has been widely used in virtually all areas, except for root canal. Root canal work until recently has been largely limited to manual instruments for various reasons. One of the main reasons is the difficulty of providing tools that can be powered by ultrasonic generators that also provide access of the tool for precision root canal work. For this reason, such tools in the past have been largely limited to manually manipulated tools and instruments, such as disclosed for example, in U.S. Pat. No. 5,026,284 issued Jun. 25, 1991 to Martin. As expressed in the background of that patent, the success of root a canal depends upon very precise and controlled preparation and shaping of the root canal.
A properly shaped root canal presents a gradually tapering cone with the narrowest part directed apically. A typical root canal is prepared by mechanical instruments used to enlarge the root canal by physically removing internal root canal tooth structure, dentin, by rotational cutting or abrasive action. These tools are tapered and pointed metal instruments with cutting edges so that the cutting occurs either on a push or pull of the stroke. With these instruments the dentist through hand manipulation prepares the canal for precise filling. The object of the preparation is to attain an apical terminus kept as small as practical in order to achieve more effective packing with greater control upon an effectively prepared seat.
Recent years have seen the proposed use of ultrasonically powered instruments for the preparation of root canals. Examples of instruments of this type are disclosed in U.S. Pat. No. 4,019,254, issued Apr. 26, 1977 to Malmin, U.S. Pat. No. 5,094,617 issued Mar. 10, 1992 to Carr and PCT Publication WO 86/05967. With the exception of the first mentioned patent, all tools are formed with a shaft tapered to a point. In the preparation of root canals, it has been found that tapered tools plug and obstructs the view of the canal wall operation from the crown area. Also, they are difficult to operate with an ultrasonic generator and provide access to remote or posterior teeth in the mouth.
The instruments of the Malmin patent are disclosed and designed for selective positioning of abrasive materials to eliminate cutting edges and thereby eliminate the need for tempering the instruments. This construction reportedly provides greater adaptability to eliminate breakage of the tools. However, it fails to provide configurations enabling it to be used with ultrasonic power units in remote or posterior areas of the mouth. In addition, it fails to provide a construction enabling the viewing of the area of cutting in the root canal.
Therefore, there is a need for an improved ultrasonic dental tool for enabling the effective root canal preparation from the crown area of the tooth.